1. Field of the Invention
The present invention relates to a plastic counterflow heat exchanger and more particularly to a counterflow heat exchanger that is inexpensive to manufacture and yet is efficient and effective.
2. Description of the Related Art
Inexpensive plastic heat exchangers are very useful because of low manufacturing cost and because such heat exchangers can be custom molded to fit specific spaces, such as those in crowded, free-standing equipment cabinets commonly used to house telecommunications equipment. In such equipment cabinets, the fluid to be cooled is air from a sealed equipment compartment. The cooling fluid, typically, is ambient air. Hence, the fluids being handled are not usually corrosive, nor is high pressure involved.
Most plastic heat exchangers are of the cross flow type as exemplified by U.S. Pat. Nos. 4,997,031 and 4,858,685; and PCT applications SE82/00393 and GB98/03368. Cross flow heat exchangers are typically constructed of rectangular panels or sheets which are stacked together and which have small projections on one of their major surfaces to space one sheet from the next. The cooled fluid enters from one side of the rectangular stack and exits from an opposite side. In a like fashion the cooling fluid enters the stack from a side 90 degrees removed from the flow of the cooled fluid and exits through an opposite side. The fluid flows alternate between sheets, and seals are provided at the corners of the stack to separate the two flows. Such seals are generally adequate in cross flow heat exchangers.
An example of a plastic counterflow heat exchanger is UK patent application No. GB 2,158,569. However, ducting to and from the heat exchanger is not addressed in the application even though it is an important consideration in the design of such units. Further, seals for plastic counterflow heat exchangers are difficult to arrange. Hence, there is still a need for effective, efficient and low cost counterflow heat exchangers.
The present invention resolves some of the problems of the related art by providing a counterflow heat exchanger comprising in combination a plurality of inner ducts forming a plurality of fluid passages, the inner ducts arranged in a stacked disposition, each of the ducts having a middle portion disposed in a first direction, and first and second end portions wherein the middle portion of each duct has a reduced depth dimension in comparison to the depth of the end portions, an outer duct mounted about the stack of inner ducts and forming with the reduced dimensioned middle portions of the inner ducts a plurality of fluid passageways disposed generally parallel to the first direction, and a first seal about the stack of first end portions and a second seal about the stack of second end portions wherein the fluid passages of the inner ducts are separated from the fluid passageways of the outer duct.
It is an object of the present invention to provide a plastic counterflow heat exchanger which is relatively simple and reliable. Another aim of the present invention is to provide a plastic counterflow heat exchanger having low tooling costs. Yet another aspect of the present invention is to provide a plastic counterflow heat exchanger which allows inexpensive custom designs and dimensions for numerous different applications. Still another aspect of the present invention is to provide a plastic counterflow heat exchanger which is efficient and effective.
A more complete understanding of the present invention and other objects, aspects, aims and advantages thereof will be gained from a consideration of the following description of the preferred embodiments read in conjunction with the accompanying drawings provided herein.